It's certainly possible it wasn't a good Paperwhite on display at the Best Buy. Still, it appeared to be working. The dictionary speed was really slow, even on my older Sony 350, my dictionary pops up almost instantly, the wait on the Kindle was excruciating in comparison. It could also simply be user error, I am not used to the Kindle interface. I think I was using a long press like I do on my T-1, rather than a double tap like the 350 uses.

You (or I, inspired by your report) have discovered an interesting behavior (or 'bug' if you prefer): when you first open a book, you cannot immediately select text with tap-and-hold. That gesture will be ignored (as will a pinch gesture to adjust text size). I don't know if this is what you found 'excruciating' but thought it was interesting to note.

But once you get one gesture out of the way ('successful' or not), all the gestures work as intended. Looking up a word is just a matter of a tap and brief hold (perhaps a third of a second, so if you say 'one thou-sand' to count off a second, you can lift after saying 'one') on the word. Nothing will happen until you lift your finger off (Kindle is waiting to see if you want to extend the selection).

On the Sony you don't have to lift your finger before stuff happens, but you still have to tap and hold. So there is some delay there as well. If I were to guess, you were holding longer than needed and thus you were simply preventing Kindle from doing your bidding.

On the unit I had, I found the settings from 1-4 much too dark to read in a completely dark room (e.g. a bedroom at night). When I compared it to my Kindle Fire, the darkest setting on the Fire was corresponding to a medium setting on the Paperwhite, while the Paperwhite's lightest setting was similar to the "medium" setting on the Fire.

Now, I understand that it does not need to be so bright, because in brightly lit rooms, the advantage of the eInk means you do not have to light it at all, but I found the lower settings much too dark for reading.

To make a long story short, for me the combination of Keyboard for summer/daytime reading and the (1st gen) Kindle Fire for nighttime reading and the dark season makes more sense, especially as the Fire was much sharper than the PW unit I received.

^ I had the 1st gen Kindle Fire, and, while I liked the interface a lot, I did not much like reading on it at night. For me, it was too heavy and too bright even at the lowest setting (I did not have Screen Dim (sp?) on it), so I returned it and went back to the K4 booklight combo.

I can understand why you might prefer to turn it all the way up (makes it easier for eyes to focus when there's more light coming into your eyes, causing your irises to contract—pinhole effect etc.) but at that point it is probably no different physiologically than reading a backlit screen in terms of messing up sleep cycles.

That is a major concern. Basically, blue and white LEDs must be avoided. I really do not know what kind of light to use with my reader to avoid messing with my sleep cycles.

Some suspect that certain people, once seeing the blobs, always see the blobs on any Paperwhite.

And many suspect Amazon sending out refurbished or returned units due to a supply shortage. Several say wipe away the colors as they just a dirty screen. But back to the OP question . Have the quality of the screens improved with the PW latest purchases ?

And many suspect Amazon sending out refurbished or returned units due to a supply shortage. Several say wipe away the colors as they just a dirty screen. But back to the OP question . Have the quality of the screens improved with the PW latest purchases ?

You will never know if the percentage of good vs bad has improved. First not a lot of Kindle owners frequent forums like this one, and then only those with issues will look for others with issues. So the few Kindle owners here, and even fewer with issues might not be by far representative for all Kindles. If for the next batch nobody complains any more, then you will know it got better. Otherwise, no.

I think the problem is rather that bright LEDs and screens make actually falling asleep more difficult and the sleep itself less restorative. At least that's what I've heard. I can't say that I have noticed an improvement since using f.lux on my monitor, but as a student I don't really have a regular sleeping schedule anyways, so it'd be difficult to notice.

I find that reading until 4 o'clock in the morning messes more with my sleep cycles than the colour of the screen...

Next time you are in front of a computer or TV screen at night, go into the color settings and bring the blue down to 0. I bet you will start yawning a few seconds later.
Scientific answers here : http://stereopsis.com/flux/research.html

^ Interesting. If true, then the Kobo Glo and Nook Glowlight would cause the same sleep deprivation, since they have a blue shine to them.

The amount of light is as important (or more so) as the hue. The Lighting Research Centre study that people keep referencing (Wood et al 2012) had to crank a full-size LCD tablet light to full brightness and expose people close-up for two hours before any significant melatonin suppression took place. The glowing frontlit devices on low are putting far, far less light into your eyes.

Out of interest, I set my Kobo Glo to high brightness, and put it next to my laptop, matched the laptop's brightness, then fiddled with the laptop's F.lux settings until they matched. A match occurred at a colour temperature of about 5400-5500: warmer than daylight, and way warmer than standard LCD settings.

Meeera, what if one reads for 4 hours or more every night? Does prolonged exposure matter at all?

I don't know if the work's been done yet. It would need to take into account real-world conditions if it is to be useful, since people don't typically sit in a dark room staring at a white document with their iPad cranked to full brightness.

I don't suppose anyone's seen data on the amount of light the frontlit readers put out at low brightness?

I don't know if the work's been done yet. It would need to take into account real-world conditions if it is to be useful, since people don't typically sit in a dark room staring at a white document with their iPad cranked to full brightness.

I don't suppose anyone's seen data on the amount of light the frontlit readers put out at low brightness?